Implementing Bitcoin and java.util.Currency

Question

I'm trying to add bitcoin as a currency to display on my site. I've got exchange rates and everything, but I keep getting an `IllegalArgumentException` whenever I use `java.util.Currency.getInstance("BTC")`. This makes sense since it's not included in the list of ISO 4217 currency codes, and also not in Java 7. I've seen a couple of options, but nothing that really solves my issue. According to the Java platform docs, you can override a specific locale's currency by creating a file `$JAVA_HOME/lib/currency.properties`. This is a problem since bitcoin is not tied to a specific locale, nor should it be used in place of any country's currency. Another similar situation was presented in this StackOverflow post, where China had a second currency code to be used, so the solution was to build your own `currency.data` file that added a second currency for the China locale. This is better, but there is still the issue of tying a currency to a locale. Has anyone run into this problem or found a…

Accepted Answer

You cannot use BTC as the currency code for bitcoins under ISO 4217. BT is reserved for Bhutan. However, ISO 3166-1 reserves several country codes for user definition. Additionally, the wiki for ISO 4217 lists `XBT` as a currency code for bitcoins (unofficially, of course).

```
Locale.Builder b = new Locale.Builder();
b.setRegion("XB");
Locale xb = b.build();
Currency bitcoin = Currency.getInstance(xb);
```

Your `currency.properties` file will look like:

```
XB=XBT,000,3
```

Unfortunately, you cannot have 8 for the minor unit because the parsing for `java.util.Currency` only handles a minor unit of `0-3`:

```
Pattern propertiesPattern = Pattern.compile("([A-Z]{3})\s*,\s*(\d{3})\s*,\s*([0-3])");
```

Implementing Bitcoin and java.util.Currency

Solution

Problem

Related problems